Embodiments include circuits, apparatuses, and systems for optical heart rate monitor light sensor amplifiers. In embodiments, an electronic circuit may include a differential amplifier having an inverting terminal, a non-inverting terminal, and an output terminal; a first variable resistance circuit coupled with a reference voltage, the inverting terminal of the differential amplifier, and the output terminal of the differential amplifier; a second variable resistance circuit coupled with the non-inverting terminal of the differential amplifier and the reference voltage; and a light sensor to generate an electrical signal in response to light reflected by skin of a user, the light sensor coupled with the non-inverting terminal and the inverting terminal of the differential amplifier. Other embodiments may be described and claimed.